This Section aims to understand the principles and mechanisms that govern intracellular calcium signalling in glial cells and neurons. Although neurons are the central players in cellular communication and information processing in the brain, recent discoveries of glial cell types, excitability and signalling properties have shown that glial cells may play an important role in long distance signalling in the brain. Glial cells do not show electrically excitable properties similar to neurons. They do, however, possess a form calcium based excitability in response to activation of neurotransmitter receptors. Most receptor mediated regulation of physiological processes utilize cellular calcium signals as triggers. In glia, like in other cells, such calcium signals have recently been recognized to have complex temporal and spatial characteristics. The research focus of the Section includes studies on the signal transduction mechanisms of various receptor systems in glial cells as well as the cell biology of calcium signalling in both glial cells and neurons. One objective is to understand cellular processes that control signal transduction mechanisms for Ca2+ signalling and cellular processes that regulate temporal and spatial signalling within cells and between cells at the molecular level. A second objective is to understand the processes that regulate calcium based excitability in glial cells resulting from neuronal activity. Thirdly, we would like to understand the changes in the signalling mechanisms that occur in reactive astrocytes during brain injury. Finally, this Section aims to describe in detail the ionic basis for cellular excitability in pineal cells.